What Are PNG Icons?

Numerous independent vendors are supplying custom icons in sizes and resolutions standard to certain systems. The article explains what icons are, how they are designed and implemented in various platforms, and what standards exist for Windows icons, Mac icons, and PNG icons.

Computer icons are an integral part of any modern GUI. Icons are small pictures of standard resolutions that visually represent objects, actions, and symbols. In graphical user interfaces, icons are used as a faster, more intuitive way to communicate with the user. Icons representing typical elements of a user interface are more visually appealing than text, can be recognized faster, and are easier for new computer users.

Originally introduced in 1970 by the Xerox Research Center and widely deployed by the Mac OS and Microsoft Windows platforms, icons make computer novices feel more comfortable with computer systems, learn faster and work more efficiently. Icons can be used to replace or supplement text commands. Commonly used in menus, toolbars, on buttons and in new ribbon-type user interfaces, icons have come a long way from the original concept.

There are multiple file formats for storing icons. Microsoft Windows systems use Windows icons in the platform-dependent ICO format. Mac OS computers store Mac icons in their specific formats, while Unix-based systems use PNG icons for most applications. As such, icon editing software is generally available for the Windows and Mac OS systems, while Unix users can design PNG icons with any image editor.

Generally speaking, icons are square pictograms that come in a number of standard sizes and color resolutions. Most systems support icons of 16x16 to 128x128 pixels, while some platforms readily accept icon images as large as 512x512 pixels. The high-resolution 512x512 pixel icons were first used in Mac OS Leopard.

Pixel dimensions of all icons are platform dependent. For example, Windows icons are specified as images in 16 and 256-color gammas as well as True Color pictures with alpha channel. Windows icons are supplied in standard resolutions of 16x16, 32x32, and 48x48 pixels. Windows Vista implements new standards for Windows icons, including icons in resolutions of up to 256x256 pixels in True Color only. Optionally, images of 128x128 and 512x512 pixels are supported. Interestingly, the high-resolution Windows Vista icons are stored in compressed PNG format instead of Windows ICO used in previous versions of Windows and for lower resolution images. Other systems such as Windows Mobile can employ standard icons of other resolutions, such as 24x24 pixels.

Many independent vendors are providing custom icons. Aha-Soft offers a wide selection of Windows icons, Mac icons, and PNG icons in all sizes and resolutions common to those systems. The company sells royalty-free icons individually and in matching sets that include icons drawn a common style or theme.

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